improves reporting of ledA/B files

Author: matejbart

app/src/main/java/org/koreader/launcher/device/lights/Rockchip3566Controller.kt

@@ -297,8 +297,15 @@ fun Rockchip3566Controller.Companion.reportApiAvailability(): String {
     logMessage.appendLine("Check read/write permissions for hardware system files")
     val ledFiles = listOf(LED_A_FILE, LED_B_FILE, MAX_LED_A_FILE, MAX_LED_B_FILE)
     ledFiles.forEach { file ->
-        logMessage.appendLine("\t${file.absolutePath} - readable: ${file.canRead()}, " +
-            "writable: ${file.canWrite()}${if (file.canRead()) " - current value: ${file.readOrElse()}" else ""}")
+        val msg = if (file.exists()) {
+            "readable: ${file.canRead()}, writable: ${file.canWrite()}${
+                if (file.canRead()) " " +
+                    "- current value: ${file.readOrElse()}" else ""
+            }"
+        } else {
+            "not available"
+        }
+        logMessage.appendLine("\t${file.absolutePath} - $msg")
     }
 
     logMessage.appendLine("Check system utility class via reflection")